Highly accurate and fast computer-controlled pan/tilt mounts have been used in the field of tracking for decades (e.g., for missile tracking U.S. Pat. No. 3,559,937, target tracking, weapon/gun mount). Tracking mounts provide for precise and fast computer control of pan/tilt position, speed and acceleration. These tracking mounts have been intrinsically complex and costly since they typically carry large payloads (e.g., greater than 20 pounds), and they position with great accuracy (e.g., 1 second arc) and speed (e.g., over 300.degree./second). The present pan/tilt tracking mount invention provides a hitherto unavailable capability for applications that have small payloads (e.g., less than 10 pounds) and which require a miniature and compact mount that can be simply controlled, and is particularly well-suited for low cost manufacture.
Recent advances in the fields of image processing, computer vision and robot vision have shown that active control of sensor pan/tilt position can facilitate and simplify computations that support a wider range of activity than a passive sensor. Advances in low cost and powerful digital signal processors (DSP), accurate and miniature solid state cameras, sensor processing algorithms, and robotics have made sensor-based control of pan/tilt position applicable to a wide range of uses, though the lack of a suitable, low cost pan/tilt mount has retarded advancements in related fields and applications. The invention disclosed herein provides the necessary tracking mount capabilities hitherto unavailable to these fields.
Motorized pan/tilt mounts have achieved widespread use in the fields of surveillance and security (e.g., U.S. Pat. Nos. 4,673,268 and 4,937,675). Often used outdoors or under harsh conditions, these mounts are often liquid-proof. These pan/tilt mounts typically achieve medium to large payload capacity with small motors by the use of large mechanical speed reductions, thus, they are generally too slow for most tracking applications. Though pulse-width modulation (PWM) and constant-current motor drivers achieve better motor performance (e.g., better acceleration, higher switching rate, better dynamic torque), most prior art security motor drivers use simpler voltage drivers due to their simplicity and historically lower cost, though advances in single chip, high-power microelectronics have made PWM constant-current drives economically competitive. Precision is not typically inherent in the prior art designs, since their mechanical speed reductions are frequently subject to backlash (e.g., as from spur gear trains), slippage (e.g., as from belt drives), and other mechanical effects. Small solid-state cameras have created a need for miniature mounts, since unobtrusiveness is desirable for surveillance and security, though current mounts are still considerably larger than their cameras, and they are not well-suited for miniature and ultraminiature realization. In addition, human and very simple automated pan/tilt controls in the prior art (e.g., joystick operation, or fixed scanning and position presets) are not generally amenable to integrated computer control of mount position in response to changes in sensor input. The pan/tilt invention disclosed herein provides hitherto unavailable capabilities in the surveillance and security fields due to its integrated computer control suitability for miniaturization/ultraminiaturization and low cost manufacture, it does not impose an upright mounting requirement (e.g., it can be mounted upside down from the ceiling for store surveillance), and its advanced tracking mount features (e.g., speed, precision, computer-control) facilitate novel surveillance and security strategies for control and computation.